Application of polyaluminium chloride in Papermaking
DATE：2017-11-02 / READ：
Application of polyaluminium chloride in Papermaking
Abstract: This paper describes the basic theory of polyaluminium chloride and polyaluminium chloride hydrolysis of morphology and composition, manufacturing method of polyaluminium chloride and its development, discuss the application and mechanism of water treatment, paper making.
Keywords: polyaluminum chloride; flocculant; sizing agent; retention and drainage agent
Polyaluminium chloride has been widely used in water treatment as an efficient flocculant for a long time. In recent years, polyaluminium chloride is also increasingly used in papermaking industry. In the early 80s, Europe developed the rosin dispersion (DRS) / poly aluminum chloride (PAC) neutral sizing system, and polymerized aluminum chloride instead of aluminum sulfate. At the same time, PAC in wet end can play a good retention and drainage effect of .
Application of 1 and PAC in papermaking industry
Polyaluminium chloride in papermaking industry in addition to the sewage treatment and water (paper), which is mainly used for rosin neutral sizing agent and retention and drainage agent, in addition, it can also be used to control the pitch and as a scavenger of anionic impurities and so on.
(1) polyaluminum chloride for rosin neutral sizing agent
Because of the worldwide shortage of resources, papermaking raw materials become more and more valuable, more cheap CaCO3 filler to as much as possible instead of fiber become more practical, so in Europe in the mid 80s pioneered the use of rosin neutral sizing technology for the production of neutral paper, the production process of the CaCO3 can be used as filler, this technology the key to success one is by polyaluminium chloride instead of alum as sizing agent. Because of the polymerization aluminum chloride in neutral or alkaline range can still maintain a positive high, while the Al2 (SO4) 3 as quickly to form Al (OH) 3 precipitation, and the pre hydrolysis of polyaluminium chloride, it is not Al2 (SO4) 3 as the pH value of the system drop very low, so, polyaluminium chloride is a new type of aluminum source ideal neutral sizing, the sizing value can reach 7.5 pH. After Europe, paper mills in North America and many other regions adopted this technology successively, making acidic papermaking as neutral papermaking. Neutral sizing not only greatly reduces the production cost by using this method, but also overcomes the use of synthetic rubber material (such as AKD) is difficult to avoid some of the shortcomings of the neutral sizing (such asslipping, is difficult to control). Even so, because of the poly aluminum chloride is in a metastable state and complex inorganic polymer, therefore, in the use of the process there are still many problems whether reasonable selection and stability of the product itself, it remains to be further research and development in the future to solve.
(2) polyaluminum chloride used as retention and drainage aids
Wet end chemistry is the study of the surface and colloid chemistry of various minor components, additives and fiber interactions in the process of dehydration and forming. In the past ten years, the main development trend of wet end chemistry is papermaking process from acidic to alkaline transition, the environment, and in recent years, another is the development trend of the chemical additives in papermaking wet end is widely used in various and adding system. China's paper industry to non wood fiber raw materials, the fiber of gramineous plants as the main raw material, because straw itself has short fibre, parenchyma cell content is high, resulting in paper strength is poor, difficult to filter water in papermaking process, thus improve its research paper and the use of various additives in alkaline conditions and keep and water filtering performance is on the wet end chemistry direction for China's national conditions.
A: retention aid
At present, many theories are considered, the tiny fiber and filler in paper retention effect mainly through both ways, namely mechanical retention and colloidal flocculation to achieve, but with the retention mechanism of the deepening of the research, that after a more important role. Mechanical retention is mainly mechanical retention in the particle structure of paper formed gradually, this mechanism is similar to the filtering effect, long fiber part of it only applies to paper material, can not explain the fines retention rate high reason, also cannot explain the retention agent retention effect.
At present, more and more research is concentrated on the fine fiber and filler retention mechanism, this study established many different concepts and models to explain the development and retention mechanism, optimize the process provides a theoretical basis for. Colloid flocculation effects include coagulation and flocculation (coagulation) (flocculation). Condensation (coagulation) refers to the use of inorganic salt or low molecular weight and charge density of high polymer to make colloidal suspension lose stability and lead to flocculation effect, the flocculation is small and densely packed sediment, it is mainly by charge neutralization and heterogeneous condensation and repair effect of several forms to achieve the.
Flocculation (flocculation) refers to a long chain polymer colloid to combine together, make the loss of stability and colloidal suspension flocculation, floc produced coarse, loose and porous mass. Flocculation mainly through flocculation and flocculation of bridged network two forms to realize.
B: filter aid
The dehydration process of paper materials will directly affect the performance of the quality of paper and paper machine, and improve the performance of water filter can improve productivity, improve sheet forming, reduce the energy consumption of drying part, so to improve the filtration performance of paper material is an important research content of wet end chemistry of A. In general, almost all of the retention agent and charge neutralization agent both the filter function, so the aluminum sulfate, polyaluminium chloride, starch, anionic polyelectrolyte and microparticle retention system can play a role of filter aid.
(3) other uses of polyaluminium chloride
With the papermaking process gradually from acidic, alkaline range in turn, increasing degree of white water closure, coated paper pulp and increase the quantity of high yield, anionic impurities in the pulp problem becomes more and more serious, if not timely treatment, it will seriously affect the operation of the paper machine and paper quality. Practice has proved that with polyaluminium chloride with high cationic charge is a good impurity capture agent, it can combine with these anionic impurities and the deposition to the fiber, thereby not only control the interference effect of anionic impurities in the pulp, but also improved the drainability of pulp, because even if the anion fiber degradation products a few will greatly affect the function of water filtration paper material.
At the same time, polymerization aluminum chloride can be easily adsorbed to the surface of the fiber, can also absorb with the negative charge of fillers and fines, making them more left inside pages; synergism with other organic polymers can effectively improve the fine material retention rate, and improve the performance of slurry water filter.
In addition, PAC can also effectively control the resin barrier, the principle of which is the same as the elimination of anionic impurities. Compared with Al2 (SO4) 3, polyaluminum chloride can fix the resin more effectively on the fiber, while the use of PAC can greatly reduce the deposition of insoluble substances such as BaSO4.
At present our country polymeric aluminum production of about 100, but the scale and industrialization of most manufacturers is not high, industrial technology is backward, product quality is not stable, which affected the development and application of the flocculant quality in a certain extent, with the recent application of inorganic polymer flocculant based on the theory of attention and the development of some plants have begun to modern production scale and international product quality transition, which will lead to polymerization of aluminum in China to further promote and application.
Polyaluminium chloride has become one of the indispensable "assistants" for environment and paper making workers in Europe and North America, and its function is almost related to water treatment and every aspect of wet end chemistry of papermaking. Therefore, only in the in-depth research, based on the analysis of polymeric aluminum chloride products reasonable selection of different performance, optimize the use conditions and operating environment, can really play a potential role of this new high aluminum source.
AUTHOR：ATZ Environmental Protection Technology